1. Technical Field
The present invention relates to a ball, and in particular a soccer ball, which comprises a top layer complex and middle and backing layer complexes. Furthermore, the present invention relates to a method of producing a top layer complex of a ball.
2. Prior Art
Various methods of producing balls are known from the prior art. In addition to the balls of a very simple construction (single-layer plastic balls), hand-sewn balls, in particular, are used in areas requiring high quality.
A known method of producing hand-sewn soccer balls, footballs, rugby balls, handballs, etc. is described, for example, in the document WO 95/09034. The construction of such a previously known ball and its production method are described below with reference to FIG. 5.
A ball 10 of the hand-sewn type is illustrated in FIG. 5. As can be seen from the figure, the ball 10 has an inflatable bladder core 9 that may consist, for example, of vulcanized latex. Located in the bladder core 9 is a valve (not illustrated) by means of which the ball can be inflated. Located on the bladder core 9 in the example illustrated are three layer complexes: a structure 12 which may consist, for example, of two or more (three in the example illustrated) fabric layers is used as backing layer complex (also known as backing complex). The different fabric layers are bonded to one another by means of suitable binding agents (usually dispersions in an aqueous solution). A layer of polyethylene foam (PE) is used as middle layer complex 13. Finally, in the example illustrated, the top layer complex 14 consists of a transparent film. In this previously known ball, the decorative markings 15 on the ball (decorations, references to the manufacturer and registered trade marks, etc.) are located between the transparent layer 14 and the layer of polyethylene foam 13.
A previously knower ball 10 of this type is produced by having the decorative markings 15 applied to the inner side of a finished transparent outer layer 14. Subsequently, the middle layer complex 13 and the backing layer complex 12 are laminated onto the printed side of the transparent covering layer 14. Subsequently, the laminate (produced over a large area) is die cut in order to produce flat shapes (the usual triangles, pentagons, hexagons) which, when joined together, result in a hollow sphere. The ball elements are then sewn together by hand. The ball skin, produced in this way, is then placed on the inflatable core 9 (in the case of a laminated ball), or the inflatable core (9) is inserted into the ball skin before it is closed, as in the case of a hand-sewn ball.
In a ball of the non-hand-sewn type, an inflatable core is wrapped with a multidirectional filament structure that is stabilized and held together by means of vulcanizable bonding. The top layer complex 14 produced according to the above method can be bonded into correspondingly provided recesses in the filament structure with the aid of a nonwoven material (a felt or mat).
However, previously known balls of this type and the production methods described have the following disadvantages: on the one hand, the trajectory properties of balls of this type are not optimum owing to the structure of the outer skin. The same applies to the bounce properties and the impact characteristics of the ball. Furthermore, a disadvantage of the production method described above consists in the fact that, because the foam layer 13 is laminated onto the printed, prefabricated film 14, the bonding of these layers to one another is not optimum, which has an adverse effect on the abrasion resistance of the markings 15. Furthermore, although the polyurethane (PU) films used for the transparent film are light stabilized, they are not lightfast. As a result, undesirable xe2x80x9cyellowingxe2x80x9d of the ball may occur as a result of the adhesive bonding. Finally, the transparent PU films have the disadvantage that they are slippery in wet conditions, and make the ball difficult to control.
One object of the present invention is therefore to provide a high quality ball and a reliable method of producing it. A ball according to the invention has optimum bounce and trajectory properties, feels xe2x80x9csoftxe2x80x9d on the foot, is fast in flight, permits optimum handling and optimum ball control, and meets or exceeds the specifications required by FIFA. Furthermore, a ball according to the invention embodies a high degree of roundness and dimensional stability, a high degree of abrasion resistance, and a low degree of water absorption.
The above mentioned problems are addressed by a ball and according to the invention, by the claimed methods of producing a top layer complex of a ball.
Specifically, the problems underlying the invention are solved by a ball, in particular by a soccer ball, whose outer skin includes a syntactic material. Syntactic materials are mixtures that consist of a matrix material into which essentially dimensionally stable, resilient bodies are dispersed.
A category of syntactic materials which are particularly preferred according to the present invention are syntactic foams which, in contrast to conventional foams, are not expanded by means of a chemical propellant or water, but by mixing in elastic, preferably spherical hollow spheres.
The microspheres that are particularly preferred according to the present invention can be procured commercially, for example under the trade name xe2x80x9cDUALITExe2x80x9d. DUALITE hollow spheres are spheres that are closed in the manner of a balloon and can be filled either with air or with another suitable gas, as a result of which, on the one hand, they are compressible and, on the other hand, assume their original shape again as soon as the pressure acting upon them diminishes. Soft microspheres of this type are extremely pressure-resistant and burst only under very high pressures.
The properties of the preferred hollow microspheres syntactic foams having excellent result in elasticity, which results in excellent bounce characteristics when they are used in balls and, in particular, in soccer balls.
Syntactic foams are known. They are used, for example, in aerospace technology, where there is a high requirement for epoxy resin or similar engineering resins as construction material. However, a disadvantage of pure epoxy resin is that it has a considerable density and thus a considerable weight. Epoxy resin cannot be foamed to reduce its weight. For this reason, consideration was given to embedding hollow glass spheres in epoxy resin in order to reduce its weight and increase its stability. Up to now, however, syntactic foams have only been used to increase the stability of the matrix material and to reduce its weight at the same time.
Up to now, no consideration has been given to using syntactic foams in outer skins of balls.
The present invention is also embodied in a method of producing a top layer complex of a ball, in particular a soccer ball, which comprises the following steps:
a) spreading a transparent liquid polymer over a backing film and subsequently solidifying the liquid polymer in order to produce a transparent layer of plastic;
b) printing a desired pattern or symbol on the solidified transparent layer of plastic;
c) spreading a second liquid polymer over the solidified, transparent and now imprinted layer of plastic and subsequently solidifying the second liquid polymer in order to produce a layer combination;
d) cutting the layer combination in order to produce ball elements; and
e) subsequently joining the ball elements together, possibly with further ball layer complexes and an inflatable bladder in order to produce the ball.
The inventive method of producing a top layer complex differs from the previously known production method in that no prefabricated transparent plastic film is used, but firstly only a high-gloss release paper over which a transparent liquid polymer is spread using a spreading knife. The liquid polymer is subsequently heat-cured in an oven and is then printed. In a second production operation, a liquid polymer is again spread over the cured transparent, printed layer and, like the first layer of plastic, is heat-cured by means of an oven.
The xe2x80x9clayeredxe2x80x9d plastic skin produced in this manner is distinguished by the fact that as a result of the particularly intimate bonding of the two layers the plastic skin behaves in such a way, with regard to its elastic properties, as if it were made of only one layer. The markings printed on the back of the first solidified layer of plastic are, so to speak, cast in by having the second liquid polymer layer spread over them and are thus sealed so that the markings are extremely resistant to abrasion against friction forces occurring within the outer skin.